1. Field of the Invention
The present invention relates to an imaging and display apparatus and method for displaying image information obtained by an imaging device on a display element.
2. Description of the Related Art
Digital cameras with an imaging device comprising image sensor such as CCD sensor or CMOS sensor have been commonly used as imaging and display apparatuses. A digital camera obtains optical images with an imaging device, and display the images on a display element such as LCD as through images, and store the images in a storage media such as a memory card as still images or moving images in response to pressing of a release button or the like.
In general, the number of pixels of a display element is less than that of an imaging element. Therefore, when displaying the through images on the display element, pixels of the imaging element is read out by means of pixel subsampling, or addition processing of pixel information is performed, in order to adapt to the number of pixels of the display element.
Many digital cameras generally have AF (Auto Focus) function and/or AE (Auto Exposure) function. A phase difference detection scheme and a contrast detection scheme are known as AF schemes. In particular, when employing the contrast detection scheme, it takes much time for AF processing if imaging frame rate of the imaging element is low.
An example method for solving the problem is shown in FIG. 12. In the example, the imaging frame rate of an imaging element is 120 fps, which is twice as high as the display frame rate of 60 fps of a display element. Spatially different image information in the vertical direction, for example, image information of odd lines (ODD) and image information of the even lines (EVEN) are alternately read out of sequential imaging frames from the imaging element, and the sequential image information is used for AF processing and AE processing. On the other hand, the display element displays images by skipping every other frame in an interlaced manner.
Another method to solve the problem is to provide two imaging elements. In a known imaging apparatus, when performing the AF processing, one imaging element is used for the AF processing and the other is used for displaying through images on a display element (for example, refer to Japanese Patent Application Laid-Open No. 2007-097033, hereinafter called patent document 1).
In the example shown in FIG. 12, however, resolution in the vertical direction become low, because the display element can display only one image information of ODD and EVEN.
On the other hand, in the display apparatus disclosed in the patent document 1, one imaging element can be driven in an appropriate imaging frame rate for the AF processing and the other can be driven in an appropriate imaging frame rate for the display frame rate of the display element, because two imaging elements are provided, and when performing the AF processing, one imaging element is used for the AF processing and the other is used for displaying a through image on the display element. Therefore, AF processing can be performed in a short time, while reduction of the resolution of the image displayed on the display element can be prevented.
However, in this case, the imaging apparatus becomes large because two independent readout control sections of the imaging elements are needed for the respective imaging elements, and it is concerned to incur cost increase.